Communication systems are deployed to facilitate communication between one or more devices, according to a pre-determined signaling process. The signaling processes often conform to a standard, whether the standard is proprietary or determined by an industry consortium. For example, wireless communication systems involve communication between a base station and a mobile unit through radio frequency (RF) transmission. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or some other modulation techniques. Example CDMA standards include (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “C.S0002-A Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 cdma2000 High Rate Packet Data Air Interface Specification” (the cdma2000 standard), and (4) others. Other wireless systems, such as GSM, AMPS, and other TDMA systems are in use throughout the world. Additional wireless standards providing for various forms of wireless data connection include the IEEE 802.11 standard and Bluetooth.
In addition to wireless standards, there are standards for communication using wires or optical fiber. Each standard differs in at least one of a variety of ways, including frequency, bandwidth, modulation format, etc., and devices that communicate according a standard must support the various properties of that standard. Devices capable of supporting more than one standard are referred to as multi-mode or multi-standard devices. New standards emerge over time, and systems supporting various standards are deployed and active. Multi-standard devices allow a user to communicate in a broader geographical area, or with a greater variety of data speeds and features, than a device supporting only a single standard with its fixed set of features, and limited geographical deployment. As an example, in the field of wireless communications, nation-wide and world-wide roaming agreements between network operators deploying heterogeneous systems are driving demand for mobile stations which support the various standards deployed in their networks.
The baseband receive section in a receiver receives baseband analog signals and performs subsequent processing before generating digital output. Analog signals coming into the baseband receiver usually undergo a filtering operation to attenuate unwanted frequencies or noise, followed by an analog-to-digital (A/D) conversion.
In the past, baseband receivers have been designed to handle a single standard. Generalizing this approach for handling multiple standards may involve creating separate signal paths corresponding to each standard supported, each with its own circuitry. A byproduct of this approach may be that separate interfaces, each requiring programming for switching between the multiple supported modes may be required. Multiple signal paths, switches, registers, and interface software add complexity, cost, and power consumption that increase with the number of standards supported.
There is therefore a need in the art for a multi-standard baseband receiver that processes incoming signals conforming to a plurality of standards or communication formats in a cost, chip area, and power effective manner, with an interface that promotes programming efficiency and minimum complexity.